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E. F. HEYDLER.

MICROPHONE.

No. 412,885. Patented Oct. 15, 1889.

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MICROPHONE.

SPECIFICATION forming part of Letters Patent No. 412,885, dated October 15, 1889.

Application filed May 8, 1889. Serial No. 310,046. (No model.)

To all whom it may concern.-

Be it known that I, EDUARD FERDINAND HEYDLER, a citizen of the Kingdom of Saxony, residing at the city of Dresden, in the Kingdom of Saxony and Empire of Germany, have invented certain new and useful Improvements in Microphones (patented to me in England April 24, 1889,N0. 6,856,) and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the letters and figures of reference marked thereon, which form a part of this specification.

The present invention relates to a so-called double microphone which is provided with two microphone elements. All parts appertaining thereto are fixed to the plates which form the diaphragm. The carbon disks are secured rigidly to these plates and the carhon-points, which are in contact with the said disks, are attached elastically thereto,

In view of the well-known facts that carbon alters its electrical resistance with the force of the pressure which is exerted upon it, and that in an inverse ratio of proportion, and that the intensity of an electrical current in a circuit in which a circuit-breaker is ineluded alters in proportion with the pressure exerted on the contact-points of the conducting parts of the circuit-breakers, two microphone elements are employed in the present invention and these are arranged in such a manner that the three carbon points of each bear with a light pressure against the carbon disks in consequence of the elastic support. In consequence of the light pressure of the points of contact and the light pressure on the carbon disks such an element offers a very great resistance to the electrical cur- As soon, however, as the pressure is increased by the vibrating movement of the diaphragm during the speaking, the resistance is decreased materially and the intensity of the current will be increased in pro portion. If the battery-currentis then passed consecutively through two such elements, these variations will be greater still, and as in each element three carbon points are in contact with the carbon disk a great resist- Patented in England April 24, 1889, No. 6,856.

ance is offered with a light pressure and a very small resistance with an increased pressure, and the variations in the intensity of the current will be much greater than if only one contact were employed.

In the accompanying drawings, Figure 1 represents a front elevation of the microphone; Fig. 2, a side elevation, and Fig. 3 a plan of the same.

To the wooden disk a, serving as the diaphragm, are screwed the carbon disks b b, which are electrically connected by a metal strip 0. Above each of these carbon disks three carbon points d cl are supported in sockets e e, fixed to the plates ff. Each of these plates ff is fastened to an india-rub ber strip 76 or by means of the clampingplate 9 or g with the screw-threaded pins h or h and the nuts 4. or t". The ends of the india-rubber strips are held in clamps Z Z of the plates m m, which latter are adj ustably supported on the standards at n by means of adjustable nuts 0 0. These standards are fixed in the diaphragm a. The battery-current is passed first through one of the plates for f to the carbon points 61 or d. From there it passes through one of the carbon disks 5 or b and through the metal strip 0 to the other carbon disk, and thence through the carbon points 01 or d of that disk and the plate f or f to the line-wire. By means of the nuts 2' e" and 0 o the pressure of the carbon points (I d on the carbon disks b b can be adjusted to a nicety.

In consequence of the standards at a being fixed to the diaphragm a all parts of the microphone must participate in the vibrations of the diaphragm during the speaking. This arrangement effectually prevents any circuit breaking, which in microphones of other construction causes the jarring and crackling sounds.

The carbon points, being supported elastically, they will always remain in contact with their carbon disks when a percussion is exerted on the diaphragm, and in consequence of this arrangement all sound-waves coming from any other source but the diaphragm will have no effect on the microphone.

1. In a microphone, the combination, with a diaphragm having two connected. contact= ICQ plates thereon, of two contacts connected by an elastic connection with the diaphragm, each of said contacts being connected with one terminal of the circuit, substantially as described.

2. In a microphone, the combination, with the diaphragm and the two connected carbon plates thereon, of two carbon contacts and a spring-support therefor, each of said contacts adapted to co-operate with one of the plates on the diaphragm, said contact-supports bein g connected to the diaphragm, substantially as described.

3. In a microphone, the combination, with a diaphragm and two connected contact-plates thereon, of two contacts mounted on the dia- I phragm and arranged to co-operate with said elastic connection, each arranged to co-operate with one of .the contact-plates, substantially as described.

5, In a microphone, the combination, with the diaphragm and a contact-plate thereon, of the standards secured to the diaphragm,

a plate adjustable on the standards, and a.

spring carrying a contact connected to the said plate, substantially as described.

6. In a microphone, the combination, with the diaphragm and the contact-plate thereon, of the standards on the diaphragm, the plate, the bowed spring connected thereto, and the contact connected to the center of the spring and co-opcrating with the contact on the diaphragm.

In witness whereof I hereunto set my hand in presence of tWo Witnesses.

EDUARD FERDINAND lIEYDLER.

lVitnesses:

RUDOLF SCHMIDT, PAUL DRUO MULLER. 

